last question 1st- your temps
the 23.3 is not bad for the cool side, but the 26.2 is quite cold for the warm side. Your snake would be happier, (and healthier) if it were about 29 to 30.
I'm not a mind reader, but in the original post the question was raised about a "Hydrometer." Hydrometers are what wine and liquor producers use to measure alcohol content. I'm assuming you are concerned with humidity which is measured with a "Hygrometer."
Most people really don't even need one with a corn snake unless they live in a very damp rain forest, or a hot dry desert. A corn snake can handle 30% to 60% with no problems. I would opt for slightly dryer over slightly wetter.
However, a "Micro Climate Setup" inside a cage is a whole new ball game, as Confined air and moisture do not condition and behave the same as free moving outdoors air. Good luck with it, but I'd be willing to bet, there's going to a constant battle in trying to keep it regulated properly.